The full-duplex communication is not a new issue, but why the current wireless networks are still half-duplex channel link, Time Division Duplex (TDD) or Frequency Division Duplex (FDD), is that because there may be a lack of feasible solutions in hardware for wireless full-duplex radio in the past. However, some research groups start and succeed to propose feasible solution and design a real full-duplex radio system in recent years.
Nowadays, the frequency band below 5 GHz has become extremely scarce, so improving spectrum efficiency or finding new frequency band is needed gradually for future wireless networks. Current wireless networks are often operating on the TDD system or the FDD system because a base station (BS) may only transmit or receive at one time and at same frequency band. When operating in a TDD system, both the transmitter and the receiver use the same frequency but transmitting operation and receiving operation are switched by time. While operating in a FDD system, two different radio frequencies are used for transmitting operation and receiving operation respectively. With the full-duplex capability, the BS can simultaneously serve an uplink client (transmitting end) and a downlink client (receiving end) at the same time and at the same frequency band, so the full-duplex networks may have the potential to double spectrum efficiency theoretically.
However, different from half-duplex networks/communication systems, a base station operating in full-duplex networks has now to serve uplink and downlink client(s) simultaneously. When a base station serves an uplink and a downlink client simultaneously, the uplink client (transmitting end) will interfere with the downlink client (receiving end). If the interference is slight, it might be still possible for the downlink client to decode its data and extract the full-duplex gain. However, if the interference is heavy, it becomes harder for the downlink client to decode its data and the full-duplex gain might be limited or even no gain could be delivered.
Therefore, it is becoming a design consideration on how to perform a data transmission for full-duplex communications in the current wireless networks or future wireless networks.